This invention relates generally to a control system for a curvilinear induction electric motor, and more particularly, to a system for controlling agitation and spin in an induction motor driven washing machine.
One problem which has confronted washing machine manufacturers has been obtaining a desirable type of agitation motion directly from the output of a low cost electric motor. In this connection, another problem has been obtaining at a low cost a range of agitation characteristics in a washing machine; from a gentle agitation required for delicate fabrics, to a vigorous agitation for heavy fabrics or heavily soiled material. Furthermore, in addition to reciprocatingly driving the agitator, the electric motor driving the washing machine must also have the capability of rapidly spinning the tub or spin basket upon completion of the washing cycle in order to spin dry clothing in the tub.
The conventional means of driving a washing machine tub and agitator is by a mechanical transmission which changes the relatively high speed rotary motion of a conventional fractional horse-power motor into the relatively slower reciprocating motion required by the agitator, and into the rotating motion required by the spin basket. A disadvantage of this conventional mechanical transmission is that it is difficult and expensive to build in a form which provides desirable washing actions from a very gentle motion to a very vigorous motion. Over the years, many attempts have been made to overcome these shortcomings, but in general these attempts have been costly and have been successful only to a limited extent.
In my co-pending patent application entitled "Electric Motor", Ser. No. 638,519, filed Jan. 5, 1976, a novel electric induction motor is disclosed which is particularly well adapted for directly driving rapidly reversible driven members such as washing machine agitators or the like. This motor has a high starting torque output and a relatively direct proportional relation between the applied voltage and available output torques. In my U.S. Pat. No. 3,914,963, which is directed to a rebound assisted reversing system for an induction electric motor, the control of tub reversal is accomplished by utilizing a mechanical elastic rebound member to trigger electrical switches in the motor drive circuit. The need remains to provide a completely electric system for controlling the rate of reversal of the output shaft rotation of the aforesaid electric induction motor, without the use of mechanical transmissions or other mechanical components.